Comparative Assessment of the NeQuick 2 and Klobuchar Models for Ionospheric Error Correction in GNSS Positioning at Equatorial West African Stations

Ionospheric propagation delay continues to affect single-frequency Global Navigation Satellite System (GNSS) positioning, particularly in equatorial regions where electron content varies across space and time. This study compared the performance of the Klobuchar and total electron content (TEC)-adapted NeQuick 2 models in reducing positioning errors at Accra (acra), Ghana, and Yamoussoukro (ykro), Côte d’Ivoire. GPS observation and navigation data from March and April 2014 were processed using the GNSS-Lab Tool (gLAB). The effective ionisation parameter (Az) was estimated hourly at ykro using a TEC data-ingestion method and applied to NeQuick 2 to derive slant TEC along satellite–receiver paths at both stations. Three solutions were assessed: uncorrected positioning, Klobuchar-corrected positioning and NeQuick 2-corrected positioning. Performance was evaluated using the 95th percentile of absolute errors in the East-West, North-South and vertical directions. At acra, vertical errors declined from 24.04 m without correction to 6.85 m with Klobuchar and 7.11 m with NeQuick 2; at ykro, the corresponding values declined from 29.65 m to 11.11 m and 10.90 m. NeQuick 2 yielded the greater East-West improvement at acra (14.11%), whereas Klobuchar produced larger North-South reductions at acra (31.83%) and ykro (27.20%). Both models substantially reduced vertical errors, but their relative horizontal performance differed by station and component. These findings support component-specific evaluation of ionospheric corrections for the two investigated stations.